1893.] Embryology. 161 
Along with the observation of normal processes, attempts were also 
made in some cases to influence these processes by increasing or dimin- 
ishing the atmospheric pressure, by placing the egg in horizontal and 
vertical positions, by surrounding them with CO, and with O; but the 
results are not definite enough to afford more than suggestions for 
future work. 
Regarding the maturation of the egg the author holds views that 
depend upon the interpretation of peculiar appearances seen in insect 
eggs, where, as is well-known, the technique is a most difficult factor. 
The first polar body receives one-half of the chromosomes, one-half 
the normal number of the ordinary cell, and also the first thelyid. 
This thelyid or “ acromatic polar body,” is a rather vague mass of 
acromatic substance including the connecting filaments and adjacent 
substances between the two separating sets of chromosomes. 
The second polar body receives the same number of chromosomes as 
the first, these being formed by a division of each, so that a half of 
each remains to form the egg nucleus; in some cases there is a second 
thelyid, but this remains inside the ovum. 
The two polar bodies may separate completely from the egg, but 
more often they remain either in protoplasmic processes of its surface 
or entirely beneath its surface; the first polar body may divide into two. 
Even when the polar bodies are extruded they may be later taken 
into the egg again. Their nuclei may undergo changes similar to that 
of the egg nucleus, either retaining the separate chromosomes or form- 
ing a chromatic network. The first and second or the product of the 
division of the first and second may fuse with one another inside the 
egg, much as the sexual pronuclei do. : 
Meanwhile numerous sperms may enter an egg; polyspermy mr 
insects has no apparent injurious results. The sperm passes into the 
yolk in a bent attitude, with the union of head and tail preceding. A 
clear area about the sperm, the arrhenoid, seems to give rise to radia- 
ting striæ in the protoplasm. This peculiar body is regarded as formed 
from the acromatic connecting filaments given to the sperm at the sec- 
ond division of its mother cell; is thus comparable, in a way, to the 
thelyid. Increase in size and change in the sperms take place simulta- 
neously in all that penetrate the yolk; only one meets and unites with 
the female pronucleus. i : 
The number of chromosomes in the nuclei of ordinary somatic cells 
and in the cleaving egg is 28, 24, 20, 18-20, 24-30, in five different 
insects studied ; the number in the first and also in second polar bodies 
in these same species, 14, 12, 10, 9, about 12. As far as studied the 
